So sorry, this is very short! But it's Castiel and explaining how your relationship began and key moments! Thank you for reading sorry for not writing lately >.<
Cas and you were always inseparable. It was a thing people could bet on if one was called the other would also come along.
You were always together.
So, let's back up a bit and talk about when he first asked you out. The first thing that pops into your mind of course was the one thing that you always tease him about. When he asked you out, you weren't sure if he was asking you out, or the wall behind you, or the ceiling above you, or the floor below you. He was looking anywhere but at your own face. It was very confusing at first, but then utterly adorable once you realized he was shy. You made this heavenly being shy.
You knew at that point you couldn't say no, in fact, you didn't want to. This Angel, wanted to date you, he wanted to love you. Did he even know what that meant? Was he sure you? Were you sure? You didn't have a lot of answers, but you did know you didn't care.
The boy you liked, liked you back and asked you out. Keeping it simple was key. Ignore all the angels and demons and hunters things and just be with Castiel.
The first time he said he loved you, is one of your fondest memories of Castiel. You and Dean and Sam were all drinking together, celebrating not dying after a dangerous hunt. Castiel was out getting beer for a bit in the middle of it, and you got a text from him.
"I love, maybe it's too soon for you, but I just wanted to let you know."
You weren't sure if he was drunk or not, him being an Angel and straight-up leaving and all, but you don't let him forget.
The first time you said you love Castiel, wasn't that night, it was a few weeks afterwards. Castiel as holding you as you watched a child's movie that you and he wanted to see. You looked up at him and he immediately said.
"Focus,"
"I am focusing,"
"On what?"
"You. I love you."
"I love you too my Angel."